1. Field of the Invention
This invention relates to a two component system useful in the preparation of curable adhesives (binders) for wood and paper products, and more particularly to a stabilized liquid composition comprising one of the components. The invention is applicable to any curable adhesives which perform physically as called for hereinafter; but inasmuch as the problem of stabilization is more prevalent with curable adhesives comprising reaction products of compounds which contain an amino (NH.sub.2) group and aldehydes, the invention will be described in their connection.
2. Description of the Prior Art
Reaction products of compounds containing an amino group and aldehydes, otherwise known and hereinafter referred to as "amino resins", are conventionally prepared by partially reacting urea or melamine or a mixture thereof with formaldehyde at an elevated temperature to produce a high viscosity plymeric form comprising methylol units. Such polymeric form, with a suitable catalyst, is combined with fibrous particles and, under heat, is further polymerized to a rigid resin.
As a result of mechanical mixing problems caused by the high viscosity of the polymeric form and the tendency of the resin particles resulting therefrom to become unduly large, or attenuated, the initial reaction to the polymeric form must be carried out under controlled conditions. Moreover, once the polymeric form has been produced, the reaction can be permaturely "triggered" to form a rigid resin even in the absence of the catalyst, by the presence of a particular combination of temperature and acidity conditions. Procedures wherein dilute urea, formaldehyde and melamine are combined with heat and then cooled to room temperatures, do not appreciably prolong the pot life of the mixture. The resin cannot be easily stored or shipped, but must be mixed in situ by the user. Individualized mixing neecs, in turn, require substantial duplication of equipment with resultant higher costs for the resin.